Variable condenser



Feb. 26, 1929.

E. a. DANIELSON VARIABLE connsnssn' Filed Dec. 13, 1926 ting/60001250? 7MW Patented Feb. 26, 1929.

UNITED, STATES ZIJBINES 'J. G. DANIELSON, OF SAN FRANCISCO, CALIFORNIA.

VARIABLE ooimnnsnn.

Application filed December 18, 1826. Serial 1T0. 154,368.

This invention relates generally to devices for tuning electricalcircuits.

In radio apparatus where close tuning of electrical circuits isessential, it has become common practice to utilize two manual controlsfor a variable tuning condenser or other tuning unit, one control beingfor coarse approximate adjustment, and the other being for fine vernierVariations. The vernier control however, is associated yvith thecondenser so that it effects a given movement of the electrodes for agiven movement of control regardless of the setting of the condenser.Thus when a condenser is used with a resonant circuit having agiveninductance, the frequency variation effected by movement of the vernierwhen the condenser is near maximum capacitance will be slight comparedto the frequency variation effected by like movement when the condenseris near minimum capacitance. For this reason, the vernier adjustment isnot sufiiciently fine for short wave lengths and is hardly noticeablefor the long wave lengths. 1

It is an object of this invention to devise a Vernier control for avariable condenser or other tuning unit which will be equally effectiveat all settings of the condenser.

It is a further object of this invention to devise a vernier control fora variable condenser which will not only be effective at all wavelengths, but will have a straight line frequency characteristic.

It is another object of this invention to devise a vernier control for avariable condenser comprising a motion transmitting mechanism adapted toautomatically change its mechanical advantage for diflerent settings ofthe condenser.

It is a further object of this invention to devise a novel form of gangcontrol for variable condensers which will incorporate a vernieradjustment.

Further objects of this invention will appear from the followingdescription in which I haveset forth the preferred embodiment of myinvention. It is tobe under-- stood that the invention is to be accordeda range of mechanical and electrical equivalents consistent with thestate of the prior art.

Referring to the drawings:

Figure lis a side elevational view of a gang control condenserincorporating the principles of this invention, the electrodes of two ofthe condensers being removed to show the operating mechanism.

Fig. 2 is a diagrammatic illustration showing the operation ofthevernier control.

Fig. 3 is a cross sectional detail view taken along the line 33 ofFig. 1. I

Fig. 4-is a top plan'view showing a portion of one of the condensers.

The invention comprises generally a special form of vernier. controlwhich may be incorporated with any of the common types of variablecondensers or variable tuning units. This vernier control consistsgenerally of a manual control member connected to a condenser electrodeor tuning element by means of a motion transmitting mechanism which isadapted to automatically change its mechanical advantage for differentsettings of the condenser. Thus when the condenser is set near itsminimum capacitance a given increment of movementof the vernier controlwill effect comparatively slight relative movement between the condenserelectrodes, while when the condenser is set for a greater capacitance,say

near its maximum value, the same incrementof movement of the verniercontrol member will effect a much greater relative movement between theelectrodes. By employing a cam as a part of the motiontransmittingmechanism the vernler may be given a Thus referring to thedrawings, there has I been shown a plurality of variable condensersnumbered 11, 12 and 13 which are adapted to tune separate circuits of aradio receiving apparatus. For example, condenser 11 may be employed totune the antenna circuit of a radio receiver while condensers 12 and 13may tune the first and second stages of a radio frequency amplifier. Forpurposes of illustration the invention has been shown as incorporatingvariable condensers of the type disclosed and claimed in my copendingapplication, Serial No. 111,193, filed May 24, 1926, and entitledVariable condenser, although it is obvious that any form of tuning unitmay be employed, whether inductive or capacitative. Such a condensercomprises a pair of relatively movable electrodes 14.- and 15, each,bore 24'. Fullcontrol of the electrodes from maximum to minimumpositions is secured by suitable control mechanism including in thismstance a manually rotatable shaft 18, to which is secured the cam 19.The electrodes 14 and 15 are adapted to move oppositely by suitablemeans such as the, intermeshing gears.

20, which are fixed with respect to the electrodes 14 and 15respectively. Motion is transmitted-from the cam 19 tothe electrodes bymeans of a lever 22 pivotally se- 25 engaging in the s iralcam groove26. It is preferable to provide a connection between the arm 22 and oneof the gears 20 which will permit an adjustment of the minimumcapacitance of each of the condensers. Suchan arrangement is shown in mycopending application to which reference has previously been made, andcomprises a member 30 adjust-ably secured to one of the gears 20 andcarrying a pin 28 slidably disposed in the slot 27 of lever 22. Member30 is provided with a slot.,32 through which extends a screw or bolt 33for clamping the member to the gear face. A pin 34 secured to the gearface also extends into slot 32 to guide the member 30. When theelectrodes are in their position of maximum. capacitance the lever 22will be in the position shown with respect to condenser 12. The slot 27is disposed in alinement with the pivotal connection 23 and pin 28 whilethe member 30 is guided in such a manner that with the condenser in thismaximum position it will slide parallel to slot 27. However, when thecondenser is in its minimum position, movement of member 30 will not beparallel to ,slot 27, with the result that when the position of thismember is adjusted, it will effect an adjustment of the minimumcapacitance of the condenser without affecting the maximum capacitance.

i 'In practice the condensers are mounted in spaced relationship upon asuitable panel 36 which may form a part of a radio cabinet or which maybe positioned behind an instrument panel 35. If the panel 36 is ofinsulating material the working parts of the condensers may be mounteddirectly thereto but if a metal panel is employed, such as shown, thecondenser parts are preferably mounted u on the individual insulatingbases 24 whlch are then secured to the panel 36 by suitable means suchas screws 37 The control shaft 18 is rotated by any convenient devicewhich is graduated to indicate the settings of the electrodes. In thedrawings there Is shown a graduated dial 38 directl mounted upon therotatable shaft 18, a though of course it is to be understood that sucha dial or other indicatin device may be mounted u on another rotata leshaft geared to the sha t 18. The cam groove 26 is preferably cut insuch a manner as to impart to the condenser a straight line frequencycharacteristic when used with a given inductance, that is, so thatangular movement of the control shaft 18 will have a linear relation tothe frequency of the circuit being timed;

I In order to secure simultaneous or gang control ofthe condensers thelevers 22 are connected to a common traversing member or bar 39. In caseof condenser 11,'since it is usually unnecessary to have vermermovecured to the condenser support 24 as by rment for one of thecondensers of a gang conmeans of pivot pin 23, and carrying a pin troltuning device, the traversing bar 39 maybe directly connected thereto asby means of pivot pin 40 engaging in extension 41 of lever 22. However,in case of the condensers 12 and 13 the connection between the traversinmember 39 and lever 22 includes a part 0 a vernier mechanism. Thusbetween bar 39 and the extension 41 there is connected a link 42 havinga pivotal connection 43 with extension '41 and a pivotal connection 44with bar 39. In order to secure vernier movement of the lever 22 andtherefore of the electrodes, the link 42 is adapted to be movedangularly with respect to the traversing member 39 by mechanism whichpreferably includes an arm 45 fixed with respect to the link 42, the arm45 engaging an actuating lever 46 pivotally mounted as at 47 One portion50 of the actuating lever 46 is adapted to-be moved by rotation of avernier control shaft 48 which has been shown as provided with a cam 49engaging a pin 51 fixed to the actuator lever 46. The other portion 52of this actuator is provided with a slot 53 within which extends a pin54 fixed to the arm 45. The actuator lever .46

is preferably biased in a direction to maintain the pin 51 in contactwith the cam 49, and for this purpose there has been shown a biasingspring 55 having its one end secured to panel 36 and its other endsecured to the actuator. 4

The operation of the vernier control may that the traversing member 39is any member movable for the purpose. of setting the electrodes at anyposition between maximum and minimum capacitance. If the link 42 remainsrelatively stationary with respect than when they are set neartheir-minimum to the traversing member 39, movement of this member willbe directly transmitted to the lever 22 and the locus of the center ofpin 54 will be substantially the same as the locus of a point upon thetraversing member 39. With the levers 22 pivoted as at 28, thetraversing bar 39 must necessarily move in a curved path and thereforethe locus of pin 54 will be a similar curve. The slot 53 is cut inportion 52 in such a manner as to coincide with this locus of pin 54 sothat when the actuator lever 46 remains stationary, movements of thetraversing member 39 will be transmitted directly to the, condenserelectrodes and link 52 will remain relatively stationary with respect tobar 39. However,

when it is desired to efl'ectvernier movement of the electrodes whilethe traversing member 39 remains fixed at a given setting, the Verniercontrol shaft 48 is rotated as by means of a knob 56, and thisrotational movement by virtue of cam 49 causes rocking of the lever 46.This movement of lever 46 moves arm 45 and therefore link 42 angularlywith respect to traversing member 39, with the result that movement isimparted to lever 22 independently of the traversing member 39. Themechanical advantage of the motion transmitting mechanism connecting thecontrol shaft 48 with the condenser electrodes depends directly upon thedistance between the centers ofpivot 47 and pin 54, this distance beingindicated in the drawing by letter a. However, when the electrodes aremoved to their position of maximum capacitance as by moving thetraversing member 39 to the left to the limit of its movement, thedistance between the pivot 47 and the pin 54 will have changed to thedistance 5. Likewise when the condenser is moved to its minimumcapacitance position the distance between centers of pivot 47 and pin 54will decrease to the value 0. Therefore it is obvious that themechanical advantage of the motive transmitting mechanism for theVernier control .varies for different settings of the condenserelectrodes and that it decreases when the capacitance of the condenseris decreased by movement of the traversing member 39.

V For a given increment of movement of the shaft 48 a much greatermovement will be imparted to the electrodes when they are set near theirmaximum capacitance value,

value. The change in the mechanical ad-. vantage is preferably made suchthat for any setting of the condenser the vernier may be made to tunethe condenser over a certain; frequency difference. By proper proper-ftioning the curvature of cam 49 this fre quency variation of the Verniercontrol is also preferably given a straight; line fre quencycharacteristic. operating the Vernier with a gang control condenser suchas shown it is obvious that movement of the dial 38 will effectsimultaneous control of all of the condensers while individual controlof shaft 48 will effect a Vernier control of either condenser 12 or 13.If it is desired to secure automatic compensating movement of theelectrodes of condensers 12 and 13 the actuator lever 46, shaft 48 andcam 49 may be omitted and a cam fixed to the panel 35 having a camsurface engaging the pin 54. By proper proportioning this cam surfacethe arm 45 and link 42 may be given sufficient movement to automaticallymaintain the circuits connected to condensers 12 and 13 in resonancerelatively movable electrical elements, control means for effectingrelative movement of said electrical elements between maximum andminimum positions, and means for effecting Vernier movements of theelectrical elements comprising a control member, and mechanisminterconnecting said member and one of said electrical elements foreffecting a lesser relative Vernier movement of the electrical elementsfor a given increment of movement of the Vernier control member forsettings of small value, than for settings of greater value.

2. A variable tuning device comprising relatively movable electricalelements, control means for effecting relative movement of saidelectrodes between positions of maximum and minimum tuning value, andmeans for effecting a Vernier movement of the elements for any settingof the elements, said means including a control member, motiontransmitting mechanism interconnecting said member with one element, andmeans for. automatically changing the mechanical advantage of saidmechanism for different settings of the elements.

3. A variable tuning device comprising relatively movable electricalelements, control means for effecting relative movement of the elementsbetween positions of maximum and minimum tuning value, and means foreffecting a Vernier movement of the elements comprising a rotatablecontrol member, and motion transmitting mechanism inmentsbetwcenpositions of maximumand:

minimum tuning value, and means a for effecting a vernier movement ofthe elements comprising-a rotatable control member, and

means operatively connecting said member and an element, including amotion transmitting lever, and means for automatically varying theeffective leverage ratio of said lever for different settings of thefirst named control means. I

5. A variable tuning device comprising relatively I movable electricalelements, a traversing member for setting said elements at positionsbetween "maximum and minimum tuning positions," motion transmittingmeans interconnecting the traversing member and .an element, and meansassociated with saidmechanism for effecting vernier control oftlieelements.

'6. A variable tuning device comprising relatively movable electricalelements, a traversing control member, motion transmitting meansconnecting said traversing member and an element whereby said elementsmay beset at any position between maximum and minimum. tuning positions,said means including a lever movable to effect vernier movement of theelements, and

a vernier control member for actuating said lever. p

7. A variable tuning device comprising relatively .movable electricalelements, a traversing control member, motion transmitting meansconnecting said traversing member and an element whereby said elementsmay be seti-at any position between 7 maximum and minimum tuningpositions, said means including a lever movable to efiect verniermovement of the elements, a vernier control member for actuating saidlever, and means for varying the amount of motion imparted to said-leverfor a given increment of movement of the control member for difierentsettings of the elements.

f8. A variable tuning device comprising relatively movable electricalelements, a traversmg control member, mechanism connectingsaidtraversing member and an element for varying the tuning value of thedevice between wide limits, said mechanism including as an elementthereof an arm'mov able to' effect a vernier adjustment of theelements,'said arm-being adapted to be bodily shifted upon movement ofsaid traversing moans member, vernier control means adapted to move saidarm to effect vernier adjustment ot the elements, said vernier controlmeans having a point of application upon the arm relativelymovablethereto upon movement of the traversing control member.

9. A variable tunlng device comprlslng a pair of relatively movableelectrical elements, control means for effecting relative vmovement ofsaid elements between positions of maximum and minimum tuning value, andmeansfor effecting vernier movement of said electrodes, said.last namedmeans including a manual control member, a lever adapted to beoscillated by said member to effect relative 'movementbetween theelements, and means for automatically varying the movement of the leverfor a given increment of movement of the control member for differentsettings of said first named control means.

10. A tuning device comprising a plurality of variable tuning unitssecured to a common support, a gang control for said units including atraversing member, alinkage connection between said member and one ofthe units movable to secure vernier control of the same, and'independentcontrol means for actuating said linkage connection.

7 11. A tuning device comprising a plurality of variable tuning unitssecured toa common support, a gang. control for said units including atraversing member, a linkage connection between said member and one ofthe units movable to secure vernier control of the same, an arm fixed'tosaid member and independent control means for actuati'ng said arm.

12. A tuning device comprising a plu'; rality of variable tuning unitssecured to a common support, a gang control for said units including atraversing member, a linkage connection between said member and one ofthe units, said connectionbeing shifted bodily upon movement of thetraversin member and being movable angularly't ct: fect'vernieradjustment of .saidunit, an arm fixed to said connection, and verniercontrol means for actuating said arm, said arm being movable relative tothe point of appli-' ber.

' Intestimony whereof, I have hereunto set my hand.

ERNEST G. DANIELSON.

